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author | Al Viro <viro@zeniv.linux.org.uk> | 2016-03-06 02:32:53 (GMT) |
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committer | Al Viro <viro@zeniv.linux.org.uk> | 2016-03-14 04:14:25 (GMT) |
commit | 5d0f49c136b520dd4da886e0e37458790f5a9617 (patch) | |
tree | ec18202cded4d0e40f1c36fcc80b801ccf86e1a5 /fs/namei.c | |
parent | 6c51e513a3aa49db87f238f96714e6cbe2d9efd5 (diff) | |
download | linux-5d0f49c136b520dd4da886e0e37458790f5a9617.tar.xz |
namei: untanlge lookup_fast()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/namei.c')
-rw-r--r-- | fs/namei.c | 83 |
1 files changed, 37 insertions, 46 deletions
@@ -1512,32 +1512,29 @@ static struct dentry *__lookup_hash(struct qstr *name, return lookup_real(base->d_inode, dentry, flags); } -/* - * It's more convoluted than I'd like it to be, but... it's still fairly - * small and for now I'd prefer to have fast path as straight as possible. - * It _is_ time-critical. - */ static int lookup_fast(struct nameidata *nd, struct path *path, struct inode **inode, unsigned *seqp) { struct vfsmount *mnt = nd->path.mnt; struct dentry *dentry, *parent = nd->path.dentry; - int need_reval = 1; int status = 1; int err; /* * Rename seqlock is not required here because in the off chance - * of a false negative due to a concurrent rename, we're going to - * do the non-racy lookup, below. + * of a false negative due to a concurrent rename, the caller is + * going to fall back to non-racy lookup. */ if (nd->flags & LOOKUP_RCU) { unsigned seq; bool negative; dentry = __d_lookup_rcu(parent, &nd->last, &seq); - if (!dentry) - goto unlazy; + if (unlikely(!dentry)) { + if (unlazy_walk(nd, NULL, 0)) + return -ECHILD; + return 1; + } /* * This sequence count validates that the inode matches @@ -1545,7 +1542,7 @@ static int lookup_fast(struct nameidata *nd, */ *inode = d_backing_inode(dentry); negative = d_is_negative(dentry); - if (read_seqcount_retry(&dentry->d_seq, seq)) + if (unlikely(read_seqcount_retry(&dentry->d_seq, seq))) return -ECHILD; /* @@ -1555,63 +1552,57 @@ static int lookup_fast(struct nameidata *nd, * The memory barrier in read_seqcount_begin of child is * enough, we can use __read_seqcount_retry here. */ - if (__read_seqcount_retry(&parent->d_seq, nd->seq)) + if (unlikely(__read_seqcount_retry(&parent->d_seq, nd->seq))) return -ECHILD; *seqp = seq; - if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) { + if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) status = d_revalidate(dentry, nd->flags); - if (unlikely(status <= 0)) { - if (status != -ECHILD) - need_reval = 0; - goto unlazy; - } + if (unlikely(status <= 0)) { + if (unlazy_walk(nd, dentry, seq)) + return -ECHILD; + if (status == -ECHILD) + status = d_revalidate(dentry, nd->flags); + } else { + /* + * Note: do negative dentry check after revalidation in + * case that drops it. + */ + if (unlikely(negative)) + return -ENOENT; + path->mnt = mnt; + path->dentry = dentry; + if (likely(__follow_mount_rcu(nd, path, inode, seqp))) + return 0; + if (unlazy_walk(nd, dentry, seq)) + return -ECHILD; } - /* - * Note: do negative dentry check after revalidation in - * case that drops it. - */ - if (negative) - return -ENOENT; - path->mnt = mnt; - path->dentry = dentry; - if (likely(__follow_mount_rcu(nd, path, inode, seqp))) - return 0; -unlazy: - if (unlazy_walk(nd, dentry, seq)) - return -ECHILD; } else { dentry = __d_lookup(parent, &nd->last); + if (unlikely(!dentry)) + return 1; + if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) + status = d_revalidate(dentry, nd->flags); } - - if (unlikely(!dentry)) - goto need_lookup; - - if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval) - status = d_revalidate(dentry, nd->flags); if (unlikely(status <= 0)) { - if (status < 0) { - dput(dentry); - return status; + if (!status) { + d_invalidate(dentry); + status = 1; } - d_invalidate(dentry); dput(dentry); - goto need_lookup; + return status; } - if (unlikely(d_is_negative(dentry))) { dput(dentry); return -ENOENT; } + path->mnt = mnt; path->dentry = dentry; err = follow_managed(path, nd); if (likely(!err)) *inode = d_backing_inode(path->dentry); return err; - -need_lookup: - return 1; } /* Fast lookup failed, do it the slow way */ |